This invention relates generally to determination of direction through magnetic direction indication, and more specifically to methods and apparatus for compensation of magnetic direction indications to account for local magnetic disturbances.
Magnetic direction indicators (e.g., magnetic compasses, magnetometers) are typically compensated to account for local disturbances in an ambient magnetic field caused by nearby magnetic objects, for example, ferrous materials, and magnetic fields generated by electrical currents. Known compensation methods are both time consuming and expensive processes. These known compensation methods also provide a limited accuracy because the methods are typically optimized for only a single angle of magnetic inclination.
Some known modem electronic compasses utilize software or firmware algorithms for magnetic compensation, but even these devices generally require time-consuming manual compensation procedures to determine a set of optimum compensation coefficients for utilization when performing the algorithms. Some low precision magnetometers are also known to exist, which provide quick automatic compensation techniques, but these techniques only provide a low accuracy compensation. Other known electronic compasses utilize biasing circuits as part of a closed loop system to attempt to reduce effects of magnetic field disturbances. However, these compasses also incorporate initialization modes, which can be complex, and which must be repeated upon each usage of the compass.